[VOL-2193] Create mocks for Kafka Client and Etcd

This commit consists of:
1) A kafka client mock that implements the kafka client interface
under voltha-lib-go/pkg/kafka/client.go
2) An embedded Etcd server that runs in-process and represents an
Etcd server.

Change-Id: I52a36132568e08c596bb4136918bebcb654a3b99
diff --git a/vendor/github.com/gorilla/websocket/conn_read.go b/vendor/github.com/gorilla/websocket/conn_read.go
new file mode 100644
index 0000000..1ea1505
--- /dev/null
+++ b/vendor/github.com/gorilla/websocket/conn_read.go
@@ -0,0 +1,18 @@
+// Copyright 2016 The Gorilla WebSocket Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build go1.5
+
+package websocket
+
+import "io"
+
+func (c *Conn) read(n int) ([]byte, error) {
+	p, err := c.br.Peek(n)
+	if err == io.EOF {
+		err = errUnexpectedEOF
+	}
+	c.br.Discard(len(p))
+	return p, err
+}